Exhaust gas cleaning system for engineering vehicle

ABSTRACT

An exhaust gas cleaning system is provided in an engineering vehicle such as a hydraulic excavator. During automatic regeneration, when a gate lock lever  5  is in a locked state and work is not performed, the exhaust gas temperature detected by the exhaust temperature detecting device  37  may be lower than the threshold value, so temperature-rising assistance is started as follows. The minimum engine output PS 1  (pump discharge pressure P 1  and pump discharge amount Q 1 ) is brought to engine output PS 2  (pump discharge pressure P 2  and pump discharge amount Q 2 ). In this way, a hydraulic load is applied to an engine to thereby increase exhaust gas temperature. When the work is resumed during the regeneration, an operator pulls down the gate lock lever to the first position A, and the engine output is returned to PS 1.  Thus, the temperature-rising assistance is stopped, however the automatic regeneration is continued.

This application is a continuation of U.S. patent application Ser. No.13/171,663, filed Jun. 29, 2011, which claims priority to Japanesepatent application No. 2010-190215, filed Aug. 27, 2010. The entirecontents of these applications are incorporated by reference herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to exhaust gas cleaning systemsfor engineering vehicles. In particular, the invention relates to anexhaust gas cleaning system for an engineering vehicle, which allows afilter to capture particulate matter contained in exhaust gas to cleanthe exhaust gas and that burns and removes the particulate mattercaptured by the filter for cleaning the filter.

2. Description of the Related Art

An engineering vehicle such as hydraulic excavator or the like has adiesel engine as its drive source mounted thereon. Regulations on thedischarge amount of particulate matter (hereinafter, called PM)discharged from the diesel engine have yearly been tightened along withthat of NOx, CO, HC, etc. To keep up with such regulations, an exhaustgas cleaning system has been known that allows a filter called a dieselparticulate filter (DPF) to capture PM to reduce the amount of the PM tobe discharged to the outside. As the amount of PM captured by the filterprogressively increases during the use of such a discharge gas cleaningsystem, the filter will be increasingly clogged. This increases theexhaust pressure of the engine to induce degradation in fuelconsumption. The PM captured by the filter is appropriately burned toremove the clogging of the filter, thereby regenerating the filter.

The filter is normally regenerated by use of an oxidation catalyst. Theoxidation catalyst is disposed on the upstream side of the filter ordirectly carried on the filter. Alternatively, the oxidation catalyst isdisposed on the upstream side of the filter and is directly carried onthe filter. In any of such cases, to activate the oxidation catalyst,the temperature of the exhaust gas has to be higher than the activatingtemperature of the oxidation catalyst. For this reason, there is atechnology called forced regeneration in which the exhaust gastemperature is increased to a set temperature (a threshold value) thatis higher than the activating temperature of the oxidation catalyst andis suitable for regeneration. The forced regeneration includes atechnique for increasing the temperature of exhaust gas by performingsub-injection (after-injection) in which fuel is injected in anexpansion stroke after direct main injection into an engine, and atechnique for increasing the temperature of exhaust gas by allowing aregeneration fuel injector installed in an exhaust pipe to inject fuelinto the exhaust gas flowing in the exhaust pipe.

The forced regeneration of the filter includes manual regeneration inwhich the regeneration is started by the operator's input and automaticregeneration in which the regeneration is automatically started. Themanual regeneration is performed as below. An amount of PM deposited ona filter (a deposition amount) is first estimated. When the PMdeposition amount reaches a PM deposition limit amount, a warning isgiven to an operator to perform the manual regeneration. Then, theoperator operates a manual regeneration switch, and the regeneration isstarted. WO 2009/60719 discloses a technology relating to manualregeneration. On the other hand, when the PM deposition amount reachesan accumulation limit value or when a predetermined time elapses, theautomatic regeneration is performed. JP-2009-79500-A discloses atechnology relating to automatic regeneration. The manual regenerationand automatic regeneration are such that the PM deposition amount isgenerally obtained by detecting an anteroposterior differential pressureon a filter and carrying out an operation based on the detected value ofsuch differential pressure.

Incidentally, there is a close relationship between engine output andexhaust gas temperature. For example, if the engine output lowers, theexhaust gas temperature lowers. When the exhaust gas temperature per seis low, even if forced regeneration is performed, satisfactoryregeneration is not likely to be performed because of insufficientlyincreased temperature. To address such a problem, JP-7-166840-A proposesan exhaust gas cleaning system attached with temperature-risingassistance means.

This exhaust gas cleaning system includes a device for detecting theneutral position of a control lever. When such a neutral detectingdevice detects the neutral position, the exhaust gas cleaning systemstarts temperature-rising assistance. When the neutral detecting devicedetects an operation position switched from the neutral position, theexhaust gas cleaning system stops the temperature-rising assistanceposition. The temperature-rising assistance means adjusts the dischargepressure and discharge amount of a hydraulic pump to increase pumpoutput and increases engine output, thereby increasing exhaust gastemperature.

SUMMARY OF THE INVENTION

As described above, the exhaust gas cleaning system in the related artstarts the temperature-rising assistance on the basis of the neutralposition of the control lever. Therefore, there is a problem (first) asbelow.

For example, when a hydraulic excavator allows a front work device towork via a control lever, its engine output is increased and alsoexhaust gas temperature is increased accordingly. On the other hand,when the control lever is made neutral, the engine output immediatelylowers while the exhaust gas temperature does not lower immediately. Theexhaust gas temperature gradually lowers. When the control lever isoperated again to resume the work, the engine output is increased andalso the exhaust gas temperature is again increased. In other words,whenever the control lever is temporarily made neutral during the work,the temperature-rising assistance is not necessarily always performed.

If the temperature-rising assistance is done unnecessarily, it is likelyto cause melting of the filter due to the abnormal increase in theexhaust gas temperature. Further, the unnecessary temperature-risingassistance is not preferable in view of energy saving.

The exhaust gas cleaning system in the related art stops thetemperature-rising assistance on the basis of the operating position ofthe control lever. Therefore, there is a problem (second) as below.

When the control lever is made neutral during the normal time, theengine becomes idle. Therefore, the engine output is brought to engineoutput PSmin (pump discharge pressure P1 and pump discharge amount Q1).When the control lever is made neutral during regeneration, to performthe temperature-rising assistance the engine output is brought to engineoutput PSmax (pump discharge pressure P2(>P1) and pump discharge amountQ2(>Q1)). Then, when the control lever is switched from the neutralposition to the operating position, the engine output is regulated tothe pump discharge pressure P1 and the pump discharge amount Q1, i.e.,to the engine output PSmin. In this way, the temperature-risingassistance is stopped.

In this case, the discharge pressure of the pump is regulated by theswitching control of a pressure control valve. In addition, thedischarge amount of the pump is regulated by the tilting control of aregulator. A response time until the pressure control valve and theregulator are operated after a control command was received occurs.Specifically, the control command may be issued so that the pumpdischarge pressure P2 becomes the pump discharge pressure P1 and thepump discharge amount Q2 becomes the pump discharge amount Q1. In such acase, they do not become P1 and Q1 immediately but the dischargepressure higher than P1 and the discharge amount greater than Q1 arekept for a given length of time.

In the state where the temperature-rising assistance is not completelystopped, if slight operation work is intended to be done via a controllever, a front work device is likely to be more driven than operator'sintention. Thus, operability is impaired. Further, if the work is doneby the front work device, an excessive load is suddenly applied to theengine to cause abrupt lowering in the rotation number of the engine(lag-down), which significantly impairs operability.

As described above, the exhaust gas cleaning system in the related arthas the problem (1) relating to the unnecessary temperature-risingassistance and the problem (2) relating to the deterioration inoperability in resuming work.

It is an object of the present invention to provide an exhaust gascleaning system that can avoid unnecessary temperature-rising assistanceand can prevent deterioration in operability in resuming work.

(1) According to the present invention, there is provided an exhaust gascleaning system for an engineering vehicle including a diesel engine, adriven body driven by power of the engine, operating means forcommanding the driven body to operate, and operation stopping means forstopping the operation of the driven body. The system includes: a filterdevice disposed in an exhaust system of the engine and including afilter for capturing particulate matter contained in exhaust gas; aregeneration device adapted to increase temperature of the exhaust gasto burn and remove particulate matter deposited on the filter; aregeneration control device adapted to control the start and stop ofoperation of the regeneration device; and temperature-rising assistancemeans for assisting temperature-rising of the regeneration device. Theregeneration control device starts the operation of thetemperature-rising assistance means when the operation stopping means isoperated to stop the operation of the driven body during the operationof the generation device.

When the operation stopping means is operated so as to stop theoperation of the driven body, a period of time during which engineoutput lowers is long. If the engine output lowers so that also theexhaust gas temperature gradually lowers, there is a high possibilitythat the exhaust gas becomes lower than a threshold value (a settemperature suitable for regeneration). In other words, unnecessarytemperature-rising assistance can be avoided by starting thetemperature-rising assistance only as necessary.

(2) Preferably, the exhaust gas cleaning system further includes anexhaust temperature detecting device adapted to detect temperature ofthe exhaust gas. The regeneration control device starts the operation ofthe temperature-rising assistance means when the operation stoppingmeans is operated to stop the operation of the driven body and theexhaust temperature detecting device detects temperature lower than athreshold value during the operation of the regeneration device.

In this way, the temperature-rising assistance is started only when theexhaust gas temperature is lower than the threshold value. Therefore,the unnecessary temperature-rising assistance can further be avoided.

(3) Preferably, the regeneration control device stops the operation ofthe temperature-rising assistance means when the operation stoppingmeans is operated to release the stop of the operation of the drivenbody.

A certain amount of time occurs until the operating means is operated todrive the driven body to resume the work after the operation stoppingmeans was operated to release the stop of the operation of the drivenbody to enable the operation thereof. Such an amount of time is longerthan a response time until the operation of the assistance means isstopped after the command of stopping the temperature-rising assistancewas issued. At the time of resuming the work, the operation of theassistance means is surely stopped. In this way, deterioration inoperability in resuming the work can be prevented.

(4) Preferably, the engineering vehicle includes a hydraulic pump drivenby the engine, and the temperature-rising means regulates at least oneof the discharge pressure and discharge amount of the hydraulic pump andapplies a hydraulic load to the engine.

(5) Preferably, the engineering vehicle includes an engine controldevice adapted to control the engine, and the temperature-risingassistance means commands the engine control device to bring therotation number of the engine to a predetermined rotation number higherthan an idle rotation number.

With the constitution just above, the engine output increases and thetemperature-rising assistance means can assist the temperature-rising ofexhaust gas during the regeneration.

(6) Preferably, the operation stopping means is a gate lock leverselectively operated between a first position where the operation of thedriven body is enabled and a second position where the operation of thedriven body is disabled.

(7) Preferably, the operation stopping means is a parking brake operatedto brake travel motion during parking of the engineering vehicle.

(8) Preferably, the operation stopping means is a shift lever switchedamong a forward movement position, a neutral position and a rearwardmovement position.

The operation of the driven body (e.g. a front work device or atraveling system) can be stopped by operating the operation stoppingmeans such as the gate lock lever, the parking lever, the shift lever,etc.

The present invention can avoid the unnecessary temperature-risingassistance and prevent the degradation in operability in resuming thework.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates the entire constitution of an exhaust gas cleaningsystem (a first embodiment).

FIG. 2 illustrates a hydraulic drive system mounted on a hydraulicexcavator.

FIG. 3 illustrates external appearance of the hydraulic excavator.

FIG. 4 illustrates a functional block diagram of a controller.

FIG. 5 is a flowchart illustrating processing contents oftemperature-rising assistance control.

FIG. 6 illustrates the relationship between the discharge pressure anddischarge amount of a hydraulic pump and the output power of an engine.

FIG. 7 illustrates exhaust gas temperature with time by way of example.

FIG. 8 illustrates the entire constitution of the exhaust gas cleaningsystem (a modified example).

FIG. 9 illustrates external appearance of a wheel loader (thirdexample).

FIG. 10 illustrates a functional block diagram of a controller.

FIG. 11 is a flowchart illustrating processing contents oftemperature-rising assistance control.

FIG. 12 is a flowchart illustrating processing contents oftemperature-rising assistance control.

DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment —Constitution—

A first embodiment of the present invention will hereinafter bedescribed with reference to the drawings.

FIG. 1 illustrates the entire constitution of an exhaust gas cleaningsystem for an engineering vehicle according to the first embodiment ofthe invention. Referring to FIG. 1, a diesel engine 1 is mounted on theengineering vehicle (e.g. a hydraulic excavator). The engine 1 isprovided with an electronic governor 1 a which is an electronic fuelinjection control unit. The target rotation number of the engine 1 iscommanded with an engine control dial 2 and the actual rotation numberof the engine 1 is detected by a rotation number detecting device 3. Theinstruction signal of the engine control dial 2 and the detected signalof the rotation number detecting device 3 are received by a controller4. The controller 4 controls the electronic governor 1 a on the basis ofthe command signal (the target rotation number) and the detected signal(the actual rotation number), thereby controlling the rotation numberand torque of the engine 1.

The hydraulic excavator is provided with a gate lock lever 5 on the leftfront side of a cab seat 108. The gate lock lever 5 can be selectivelyoperated between a first position A which is a lowered position to limitan entrance to the cab seat 108 and a second position B which is araised position to open the entrance to the cab seat 108.

The exhaust gas cleaning system is disposed on an exhaust pipe 31constituting part of an exhaust system of the engine 1. The exhaust gascleaning system includes: a DPF device 34 including a filter 32collecting particulate matter contained in exhaust gas and oxidationcatalyst 33 disposed on the upstream side of the filter 32; a positiondetecting device 35 detecting the operating position of the gate locklever 5; and a differential pressure detecting device 36 detectinganteroposterior differential pressure (a pressure loss of the filter 32)between the upstream side and downstream side of the filter 32. Thecleaning system further includes an exhaust temperature detecting device37 installed on the upstream side of the filter to detect thetemperature of exhaust gas; a regeneration switch 38 instructing manualregeneration; and a regeneration fuel injection device 39 installed onthe exhaust pipe 31 between the engine 1 and the DPF device 34. Theoxidation catalyst 33 and the regeneration fuel injection device 39constitute a regeneration unit which burns and removes the PM(particulate matter) deposited on the filter 32 for regenerating thefilter 32.

FIG. 2 illustrates the hydraulic drive system mounted on the engineeringvehicle (e.g. a hydraulic excavator). The hydraulic drive systemincludes: a variable displacement main hydraulic pump 11 and a fixeddisplacement pilot pump 12 which are driven by the engine 1; a pluralityof actuators including a hydraulic motor 13 and hydraulic cylinders 14and 15, the motor 13 and the cylinders 14 and 15 being driven by thehydraulic fluid discharged from the hydraulic pump 11; and a pluralityof flow control valves including pilot-operated flow control valves 17to 19 which control the flow (a flow rate and a direction) of thehydraulic fluid supplied from the hydraulic pump 11 to the hydraulicmotor 13 and hydraulic cylinders 14 and 15. The hydraulic drive systemfurther includes a pilot relief valve 21 which regulates the pressure ofthe hydraulic fluid discharged from the pilot pump 12 and forms a pilothydraulic source 20; a main relief valve 22 which sets the upper limitof the discharge pressure of the main hydraulic pump 11; a control valve30 installed on the downstream side of a center bypass line connectingthe flow control valves 17 to 19 in series. The hydraulic drive systemfurther includes a solenoid selector valve 23 connected to thedownstream side of the pilot hydraulic source 20 and on/off controlleddepending on the opening/closing state of the gate lock lever 5installed at the cab seat entrance of the hydraulic excavator; andremote control valves 25, 26 and 27. The remote control valves areconnected to a pilot fluid passage 24 on the downstream side of thesolenoid selector valve 23 and produces control pilot pressures a, b; c,d; e and f, respectively, adapted to operate the flow control valves 17to 19 using the hydraulic pressure of the pilot hydraulic source 20 asoriginal pressure.

The remote control valves 25, 26 and 27 are operated by thecorresponding left and right control levers 28 and 29 installed on theleft and right of the cab seat 108. The control levers 28 and 29 caneach be operated in a cross shape direction. When the control lever 28is operated in a one direction of the cross shape, the remote valve 25is operated. When the control lever 28 is operated in the otherdirection of the cross shape, the remote control valve 27 is operated.When the control lever 29 is operated in a one direction of the crossshape, the remote control valve 26 is operated. When the control lever29 is operated in the other direction of the cross shape, a remotecontrol valve not illustrated is operated. In the case where the controllever 28 is operated in the one direction of the cross shape, when it isoperated from the neutral direction in the one direction, the remotecontrol valve produces control pilot pressure “a” and when the controllever 28 is operated from a neutral position in the opposite direction,the remote control valve 25 produces control pilot pressure “b”. Thecontrol pilot pressures “a” and “b” are led via pilot lines 25 a and 25b to the corresponding pressure-receiving portions of the flow controlvalve 17, whereby the flow control valve 17 is switched from the neutralposition.

Similarly, in the case where the control lever 28 is operated in theother direction of the cross shape, when it is operated in the onedirection from the neutral position, the remote control valve 27produces control pilot pressure “e”, and when the control lever 28 isoperated in the opposite direction from the neutral direction, theremote control valve 27 produces control pilot pressure “f”. The controlpilot pressures “e” and “f” are led via pilot lines 27 a and 27 b to thecorresponding pressure-receiving portions of the flow control valve 19,whereby the flow control valve 19 is switched from the neutral position.In the case where the control lever 29 is operated in the one directionof the cross shape, when it is operated from the neutral position in theone direction, control pilot pressure “c” is produced, and when the flowcontrol lever is operated from the neutral direction in the oppositedirection, control pilot pressure “d” is produced. The control pilotpressures “c” and “d” are led via pilot control lines 26 a and 26 b,respectively, to the respective pressure-receiving portions of the flowcontrol valve 18, whereby the flow control valve 18 is switched from theneutral position.

The control pilot pressures a to f are subjected to communication orshutoff depending on the position of the gate lock lever 5.

When the gate lock lever 5 is at the first position A, the solenoid ofthe solenoid selector valve 23 is energized to switch the solenoidcontrol valve 23 from the position illustrated in the figure. In thisway, the pressure of the pilot hydraulic source 20 is led to the remotecontrol valves 25, 26 and 27, which makes it possible to allow theremote control valves 25, 26 and 27 to operate the corresponding flowcontrol valves 17, 18 and 19. When the gate lock lever 5 is operativelyraised to the second position B, the solenoid of the solenoid selectorvalve 23 is de-energized to switch the position illustrated in thefigure, thereby blocking the communication between the pilot hydraulicsource 20 and the remote control valves 25, 26 and 27. This makes itimpossible for the remote control valves 25, 26 and 27 to operate thecorresponding flow control valves 17, 18 and 19. In short, when the gatelock lever 5 is operatively raised to the second position B, the remotecontrol valves 25, 26 and 27 (control lever units) are brought into alocked state. When the gate lock lever 5 is operatively lowered to thefirst position A again, the remote control levers 25, 26 and 27 arebrought into an unlocked state. The switching of the position of thesolenoid valve 23 by the gate lock lever 5 is done as below. Forexample, a switch not illustrated in the figure is installed between thesolenoid of the solenoid selector valve 23 and the power supply. Whenthe gate lock lever 5 is at the first position A, such a switch isturned on (closed) to energize the solenoid. When the gate lock lever 5is operated to be at the second position B, the switch is turned off(opened) to de-energize the solenoid.

The control valve 30 is a two-position selector valve having an openposition and a close position. When the solenoid is not energized, thecontrol valve 30 is at the open position. When the solenoid isenergized, the control vale 30 is switched from the open positionillustrated from the close position.

FIG. 3 illustrates external appearance of the hydraulic excavator. Thehydraulic excavator includes a lower travel structure 100, an upperturning body 101, and a front work device 102. The lower travelstructure 100 has left and right crawler type travelling devices 103 aand 103 b which are driven by left and right travelling devices 104 aand 104 b, respectively. The upper turning body 101 is mounted on thelower travel structure 100 so as to be turnable by a turning motor 105.The front work device 102 is mounted onto the front portion of the upperturning body 101 so as to be able to be laid and raised. The upperturning body 101 is provided with an engine room 106 and a cabin 107. Anengine 1 is disposed in the engine room 106. The gate lock lever 5(FIG. 1) is installed at the entrance to the cab seat 108 in the cabin107. The control lever units (not illustrated) incorporating thecorresponding remote control levers 25, 26 and 27 are disposed on theleft and right of the cab seat 108.

The front work device 102 is of an articulated structure having a boom111, an arm 112 and a bucket 113. The boom 111 is turned vertically bythe extension and contraction of a boom cylinder 114. The arm 112 isturned upward and downward, and forward and rearward by the extensionand contraction of an arm cylinder 115. The bucket 113 is turned upwardand downward, and forward and rearward by the extension and contractionof a bucket cylinder 116.

In FIG. 2, the hydraulic motor 13 corresponds to e.g. the turning motor105. The hydraulic cylinder 14 corresponds to e.g. the arm cylinder 115.The hydraulic cylinder 15 corresponds to e.g. the boom cylinder 114. Thehydraulic drive device illustrated in FIG. 2 is provided with otherhydraulic actuators and control valves corresponding to the travelingmotors 104 a, 104 b and the bucket cylinder 116, etc. However, theirillustrations are omitted.

—Control—

FIG. 4 illustrates a functional block of the controller 4. Thecontroller 4 includes a main controller 41 and an engine controller 43,which are connected with each other via a communication line 44 to forma vehicle-body network. The main controller 41 is adapted to receive thecommand signal of the engine control dial 2, the detection signals of aposition detecting device 35, of a differential pressure detectingdevice 36 and of an exhaust temperature detecting device 37. The enginecontroller 43 is adapted to receive the detection signal of a rotationnumber detecting device 3.

The engine controller 43 receives the command signal of the enginecontrol dial 2 via the communication line 44 and controls the rotationnumber and torque of the engine 1 on the basis of the command signal andthe detected signal of the rotation number detecting device 3.

The main controller 41 controls the vehicle body in general such as thehydraulic drive device, etc. For example, the main controller 41controls the discharge pressure and discharge amount of the hydraulicpump 11 by controlling the control valve 30 and the regulator of thehydraulic pump 11. Regeneration control and temperature-risingassistance control are each one function of the main controller 41.

The main controller 41 receives the detected signal of the differentialpressure detecting device 36, estimates a PM deposition amount, andexecutes arithmetic processing on regeneration control on the basis ofthe estimated PM deposition amount. The main controller 41 then sends acontrol signal corresponding to the calculation result to the enginecontroller 43 via the communication line 44. In response to the controlsignal, the engine controller 43 controls the electronic governor 1 aand the regeneration fuel injection device 39 (automatic regenerationcontrol). The main controller 41 receives an instruction signal of theregeneration switch 38 and executes the arithmetic processing on theregeneration control (manual regeneration control).

A description is given of the temperature-rising assistance control bythe main controller 41. The main controller 41 receives the detectedsignals of the position detecting device 35 and of the exhausttemperature detecting device 37 and executes arithmetic processing onthe temperature-rising assistance control on the basis of the detectedsignals. The main controller 41 sends the control signals correspondingto the calculation results to the control valve 30 and the regulator ofthe hydraulic pump 11 to control the discharge pressure and dischargeamount of the hydraulic pump 11. In this way, the load on the engine 1driving the hydraulic pump 11 is increased to increase the exhaust gastemperature of the engine 1.

FIG. 5 is a flowchart illustrating the processing contents of thetemperature-rising assistance control by the main controller 41.

The main controller 41 first determines whether or not the maincontroller 41 per se is executing the regeneration control (step S10).When determining that the regeneration control is being done, the maincontroller 41 determines whether or not the gate lock lever 5 isoperatively raised to the second position B on the basis of the detectedsignal of the position detecting device 35. In other words, the maincontroller 41 determines whether or not the gate lock lever 5 is in thelocked state where the control pilot pressure is blocked (step S20).When determining that the gate lock lever 5 is in the locked state, themain controller 41 determines whether or not the exhaust gas temperatureis lower than a threshold value (a set value suitable for regeneration)on the basis of the detected signal of the exhaust temperature detectingdevice 37 (step S30). When determining that the exhaust gas temperatureis lower than the threshold value, the main controller 41 controls thedischarge pressure and discharge amount of the hydraulic pump 11 andapplies a hydraulic load to the engine 1, thus starting thetemperature-rising assistance (step S40).

In step S10, the main controller 41 may determine that it does notexercise the regeneration control. In step S20, the gate lock lever 5may not be in the locked state (is at the first position A). In stepS30, the exhaust gas temperature may not be lower than the thresholdvalue (the temperature suitable for the regeneration). In any of suchcases, the processing is returned to the procedure immediately after thestart and the procedures of steps S10, S20 and S30 are repeated.

The start of temperature-rising assistance in step S40 is performed asbelow for example. FIG. 6 illustrates the relationship between thedischarge pressure and discharge amount of the hydraulic pump 11 and theoutput power of the engine 1. When, during normal times, the gate locklever 5 is in the locked state and work is not done, the dischargepressure and discharge amount of the hydraulic pump 11 are controlled topump discharge pressure P1 and pump discharge amount Q1, respectively,in view of energy saving to provide minimum engine output PS1. When thetemperature-rising assistance command is issued, the discharge pressureand discharge amount of the hydraulic pump 11 are controlled to pumpdischarge pressure P2(>P1) and pump discharge amount Q2(>Q1),respectively. The engine 1 is allowed to have engine output PS2 fordriving the hydraulic pump 11, that is, the load on the engine 1 isincreased, thereby increasing the exhaust gas temperature of the engine1.

After the start of temperature-rising assistance, determination is madeas to whether or not at least one of the determination in step 10(condition 1), the determination in step 20 (condition 2) and thedetermination in step 30 is negative (at least one of the conditions 1to 3 is not satisfied) (step 50). When it is determined that any one isnegative, the temperature-rising assistance is stopped (step S60).

The stop of the temperature-rising assistance in step S60 is carried outby controlling the pump discharge pressure and pump flow rate to thepump discharge pressure P1 and pump discharge amount Q1, respectively,to provide the minimum engine output PS1. The load on the engine 1 isreduced to lower the exhaust gas temperature of the engine 1.

When it is determined that all of conditions 1 to 3 is affirmative (allof the conditions 1 to 3 is satisfied. In other word, none of theconditions 1 to 3 is negative.) in step S50, the procedure of step 50 isrepeated to continue the temperature-rising assistance.

—Operation—

A description is given of the operation of the exhaust gas cleaningsystem according to the first embodiment. FIG. 7 illustrates an examplein exhaust gas temperature with time for assisting understanding.

When the engineering vehicle (the hydraulic excavator) finishes work, anoperator operatively raises the gate lock lever 5 from the firstposition A to the second position B to bring it into the locked state.In this case, when the PM deposition amount reaches an accumulationlimit value, automatic regeneration is started. There is also a casewhere, since the automatic regeneration is started during work, anoperator interrupts the work and brings the gate lock lever 5 into thelocked state.

In general, exhaust gas temperature immediately after work or duringwork is higher than the activating temperature of the oxidation catalyst33. When the regeneration fuel injection device 39 is controlled toinject fuel into the exhaust pipe 31, unburned fuel is supplied to andoxidized by the oxidation catalyst 33 to provide reaction heat. Suchreaction heat further increases the exhaust gas temperature to burn andremove the PM deposited on the filter 32.

In this case, the exhaust gas temperature detected by the exhausttemperature detecting device 37 is equal to or higher than a thresholdvalue. Therefore, the temperature-rising assistance is not performed(step S10→S20→S30→S10) (the state 1 in FIG. 7).

The gate lock lever 5 is usually in the locked state. When work is notperformed, the discharge pressure and discharge amount of the hydraulicpump are controlled to the pump discharge pressure P1 and the pumpdischarge amount Q1, respectively, in view of energy saving to providethe minimum engine output PS1. If the engine output is lowered, also theexhaust gas temperature lowers gradually and becomes lower than thethreshold value. In this case, even if the forced regeneration isperformed, there is a possibility that the exhaust gas temperature maynot sufficiently be increased (state 2 in FIG. 7).

Therefore, when the exhaust gas temperature detected by the exhaust gastemperature device 37 is lower than the threshold value, thetemperature-rising assistance is started (step S10→S20→S30→S40). Thedischarge pressure and discharge amount of the hydraulic pump arecontrolled to the pump discharge pressure P2 and the pump dischargeamount Q2, respectively, to provide engine output PS2, which increasesexhaust gas temperature (state 3 in FIG. 7).

After the start of the temperature-rinsing assistance, when the exhaustgas temperature is equal to or higher than the threshold value by thetemperature-rising assistance or when the automatic regeneration isfinished by burning and removing the PM, the temperature-risingassistance is stopped (Step S40→S50→S60).

On the other hand, in a case where work is resumed during theregeneration, when the operator operatively pulls down the gate locklover 5 to the first position A, the temperature-rising assistance isstopped (Step S40→S50→S60) (state 4 in FIG. 7).

Incidentally, even if the temperature-rising assistance is stopped byoperatively pulling down the gate lock lever 5, automatic regenerationis continued. If the operator operatively pulls down the gate lock lever5 to the first position A and resumes the work, the engine output isincreased so that the exhaust gas temperature is equal to or higher thanthe threshold value. Thus, satisfactory regeneration is performed (state5 in FIG. 7).

—Advantages—

A description is given of the effects of the exhaust gas cleaning systemaccording to the first embodiment.

(a) The exhaust gas cleaning system in the related art starts thetemperature-rising assistance on the basis of the neutral position ofeach of the control levers 28 and 29. When the control levers 28 and 29are made neutral, the engine output is lowered. However, if the controllevers 28 and 29 are operated again to resume the work, the engine workis increased again so that it is not likely that the exhaust gastemperature becomes lower than the threshold value. In other words, ifthe period of time during which the engine output is lowered is short,it is not necessary to perform the temperature-rising assistance. On theother hand, if the temperature-rising assistance is performedneedlessly, there is a possibility that the filter is damaged by meltingdue to abnormally increased temperature. In addition, such needlesstemperature-rising assistance is not preferable also in view of energysaving.

The exhaust gas cleaning system according to the present embodimentstarts the temperature-rising assistance on the basis of the operatingposition (the second position B) of the gate lock lever 5. Whenoperatively raising the gate lock lever 5 to the second position B, theoperator often gets away from the hydraulic excavator for a rest.Therefore, the period of time during which the engine output is loweredis long. If the engine output is lowered, also the exhaust gastemperature gradually lowers and is more likely to become lower than thethreshold value. In short, the exhaust gas cleaning system according tothe present embodiment starts the temperature-rising assistance onlywhen required. Thus, the unnecessary temperature-rising assistance canbe avoided.

(b) If the engine output is lowered, the exhaust gas temperaturegradually lowers; however, it will not lower immediately. If the exhaustgas temperature is equal to or higher than the threshold value, thetemperature-rising assistance is not necessary. The exhaust gas cleaningsystem according to the present embodiment is provided with the exhausttemperature detecting device 37. When the exhaust gas temperaturedetected by the exhaust temperature detecting device 37 is equal to orhigher than the threshold value, the temperature-rising assistance isnot performed. Thus, the unnecessary temperature-rising assistance canfurther be avoided.

(c) The exhaust gas cleaning system in the related art has the followingsame operation with the exhaust gas cleaning system according to thepresent embodiment. Both the systems control the discharge pressure anddischarge amount of the hydraulic pump 11 and increase the engine outputPS1 (the pump discharge pressure P1 and the pump discharge amount Q1) tothe engine output PS2 (the pump discharge pressure P2 and the pumpdischarge amount Q2). In this way, the systems start thetemperature-rising assistance and return the engine output PS2 to theengine output PS1 (the pump discharge pressure P1 and the pump dischargeamount Q1) and stop the temperature-rising assistance.

In this case, the discharge pressure of the pump 11 is regulated by theswitching control of the control valve 30. In addition, the dischargeamount of the pump 11 is regulated by the tilting control of theregulator. Response time occurs until the control valve 30 and theregulator of the pump 11 are operated after a control command wasinputted. In other words, even if the control order is issued so that P2and Q2 become P1 and Q1, respectively, P2 and Q2 do not immediatelybecome P1 and Q1, respectively. Therefore, discharge pressure higherthan P1 and a discharge amount greater than Q1 are kept for a givenlength of time.

The exhaust gas cleaning system in the related art commands the stop ofthe temperature-rising assistance on the basis of the operatingpositions of the control levers 28 and 29. There is no time until thework is resumed by the control levers 28 and 29 after thetemperature-rising assistance was stopped by the control levers 28 and29. Therefore, if the work is resumed in this state, operability islikely to deteriorate.

The exhaust gas cleaning system in the present embodiment commands thestop of the temperature-rising assistance on the basis of the operatingposition (the first position A) of the gate lock lever 5. An interval oftime from the command of stopping the temperature-rising assistance tothe resuming of the work by the operative levers 28 and 29, i.e., aninterval of time until the operator operates the control levers 28 and29 after the operator operatively pulls down the gate lock lever 5 toenable the operation of the hydraulic excavator, is longer than theresponse time of the control valve 30 and of the regulator of the pump11. Therefore, the engine output is returned to the engine output PS1(the pump discharge pressure P1, pump discharge amount Q1) at the timeof resuming the work. Thus, it is possible to prevent operability fromdeteriorating at the time of resuming the work.

MODIFIED EXAMPLE

The embodiment of the present invention has been described thus far.However, the present invention is not limited to this. The invention canbe modified in various ways within the scope of the spirit thereof. Thefollowing recites such modified examples.

1. In the operation of the present embodiment, the description is givenon the premise of the automatic regeneration control. However, thetemperature-rising assistance may be done during manual regenerationcontrol. The manual regeneration control is started based on the commandof a regeneration switch 38.

2. In the operation of the present embodiment, the automaticregeneration is stated when the PM deposition amount estimated by thedifferential pressure detecting device 36 reaches the accumulation limitvalue and is ended when the PM is burned and removed so that theestimated PM deposition amount becomes equal to or less than theaccumulation permissible value. However, the automatic regeneration maybe started after a predetermined time elapses and may be ended after apredetermined time elapses.

3. In the operation of the present embodiment, the PM deposition amountis obtained by detecting the anteroposterior differential pressure onthe filter by the differential pressure detecting device 36 and byperforming a calculation based on the detected value of the differentialpressure. However, the PM deposition amount may be obtained as below.The engine 1 is provided with an air-quantity detecting device 51 whichdetects a quantity of air flowing into the engine and with a boostpressure detecting device 52 which detects the pressure of air flowinginto the engine. The quantity and pressure of the air flowing into theengine are detected by such devices and a calculation is performed basedon the detected values. FIG. 8 illustrates the entire constitution ofthe exhaust gas cleaning system for an engineering vehicle according tothis modified example.

4. In the operation of the present embodiment, as illustrated in thefunctional block diagram (FIG. 4) of the controller 4, the control valve30 and the regulator of the hydraulic pump 11 directly receive thecommand signals outputted from the controller 4 and are controlled basedon the command signals. However, another constitution as below may bepossible. Solenoid valves are installed. The controller 4 sends commandsignals to these solenoid valves. The solenoid valves are each switchedbased on the command signals and produce control pilot pressure takingthe hydraulic pressure of the pilot hydraulic source 20 as sourcepressure. The control valve 30 and the regulator of the hydraulic pump11 are each controlled based this control pilot pressure.

Second Embodiment

In the first embodiment, the control valve 30, the regulator of the pump11 and one function of the main controller 41 controlling theseconstitute the temperature-rising assistance means as below. Thedischarge pressure and discharge amount of the hydraulic pump 11 areadjusted and the hydraulic load is applied to the engine 1 to assisttemperature-rising during regeneration. However, the temperature-risingassistance means is not limited to this.

The constitution of a second embodiment is the same as that of the firstembodiment; therefore, its illustration is omitted. The secondembodiment is different from the first embodiment in the details of thestart (S40) and stop (S60) of the temperature-rising assistance in thetemperature-rising assistance control (see FIG. 5) of the maincontroller 41.

The start of the temperature-rising assistance in step S40 is done asbelow for example.

During the normal time, the gate lock lever 5 is in the locked state.When work is not done, the engine controller 43 controls the rotationnumber of the engine 1 to the idle rotation number NO (low rotationnumber) in view of energy saving (automatic idle control). Duringregeneration, when exhaust gas temperature is insufficient,temperature-rising assistance is performed.

The main controller 41 switches the target rotation number of the engine1 from the target rotation number (the idle rotation number NO) directedby the engine control dial 2 to a predetermined rotation number N1. Inaddition, the main controller 41 sends the target rotation number (therotation number N1) to the engine controller 43 via the communicationline 44. The engine controller 43 exercises feedback control on a fuelinjection amount of the electronic governor 1 a on the basis of thetarget rotation number (the rotation number N1) and the actual rotationnumber of the engine 1 detected by the rotation number detecting device3 so that the rotation number of the engine 1 may become the firstrotation number N1. The rotation number N1 is one suitable for theregeneration control that can raise the temperature of the exhaust gasat that time to temperature higher than the activating temperature ofthe oxidation catalyst 33. For example, the rotation number N1 is amiddle-speed rotation number, e.g., approximately 1800 rpm.

The stop of the temperature-rising assistance in step S60 is done bycontrolling the rotation number of the engine 1 to the idle rotationnumber NO (the low-speed rotation number). The load on the engine 1 isreduced to lower the exhaust gas temperature of the engine 1.

Also the present embodiment configured as described above can producethe effects (a), (b) and (c) of the first embodiment.

Third Embodiment

In the first embodiment, the engineering vehicle is the hydraulicexcavator. The gate lock lever 5 constitutes operation stopping meansfor disabling the operation of the front work device 102 of thehydraulic excavator to stop the operation. However, the operationstopping means for the engineering vehicle is not limited to this.

A third embodiment is described with reference to FIGS. 9 to 12. Thepresent embodiment is such that the present invention is applied to awheel loader.

FIG. 9 illustrates the external appearance of the wheel loader which isan engineering vehicle according to the present embodiment. In FIG. 9,the wheel loader 200 includes a vehicle-body front portion 201 and avehicle-body rear portion 202 which are turnably pin-joined to eachother and which constitute a vehicle body. A front work device 204 isinstalled on the vehicle-body front portion 201. A cab seat 206 isinstalled on the vehicle-body rear portion 202. The cab seat 206 isprovided with operation means such as a control lever device 207, asteering wheel 208 and the like. The vehicle-body front portion 201 andthe vehicle-body rear portion 202 are provided with front wheels 235 andrear wheels 236, respectively. In addition, an engine 1, a hydraulicpump 11, a controller 4 and other devices are mounted on thevehicle-body rear portion 202. The front wheels 235 and the rear wheels236 are connected to an output shaft of the engine 1 via a torqueconverter and a transmission not illustrated to constitute a travelingsystem (not illustrated). When the operator depresses an acceleratorpedal 61 (described later), the rotation number and torque of the engine1 are increased. Such power is transmitted to the front wheels 235 andrear wheels 236 via the torque converter and the transmission to providetravel motion. A steering cylinder 203 is installed between thevehicle-body front portion 201 and the vehicle-body rear portion 202.The steering wheel 208 is operated to actuate the steering cylinder 203to change the direction of the vehicle-body front portion 201 (thetraveling direction of the vehicle body) with respect to thevehicle-body rear portion 202.

The wheel loader further includes operating means such as an acceleratorpedal 61 which outputs command signals for controlling the rotationnumber and torque of the engine 1 and traveling speed; parking brakingmeans such as a parking brake 62; and a shift lever 63 selectivelyswitched among a forward movement position F, a neutral position N and arearward movement position R.

FIG. 10 illustrates a functional block of a controller 4.

A command signal of the accelerator pedal 61 is received by a maincontroller 41 of the controller 4. The main controller 41 calculates thetarget rotation number of the engine 1 on the basis of the commandsignal. The main controller 41 sends a control signal corresponding tothe calculation result to an engine controller 43 via a communicationline 44. The engine controller 43 controls an electronic governor 1 a onthe basis of the target rotation number and the detected signal (theactual rotation number) of the rotation number detecting device 3 tocontrol the rotation number and torque of the engine 1. The output shaftof the engine 1 is connected to a traveling system. The enginecontroller 43 controls the rotation number and torque of the engine 1 tocontrol traveling speed.

In the present embodiment, for example, if temperature-rising assistanceis started based on a non-operation state of the accelerator pedal 61, aproblem associated with unnecessary temperature-rising assistanceoccurs. If the temperature-rising assistance is stopped based on theoperation state of the accelerator pedal 61, a problem associated withdeterioration in the operability in resuming traveling occurs.

The parking brake 62 is provided with a parking brake operating positiondetecting device 66 which detects the operating position thereof. A maincontroller 41 receives a detected signal of the parking brake operatingposition detection device 66. The main controller 41 exercises brakingcontrol on the wheel loader on the basis of its command signal. Whenbeing operated to be at the braking position, the parking brake 62disables the traveling of the wheel loader to stop its operation.

The shift lever 63 is provided with a shift lever operating positiondetecting device 67 which detects the operating position thereof. Alsothe detected signal of the shift lever operating position detectingdevice 67 is received by the main controller 41. The main controller 41exercises switching control on switching among forward movement, neutraland rearward movement on the basis of its command signal. When beingoperated to be at a neutral position N, the shift lever 63 disables thetraveling of the wheel loader to stop its operation.

The parking brake 62 and the shift lever 63 each constitute operationstopping means.

FIG. 11 and FIG. 12 are flowchart illustrating processing contents oftemperature-rising assistance control by the main controller 41 in thepresent embodiment. The flowchart of FIG. 11 is different from that ofFIG. 5 in that a determination relating to the operating position of theparking brake 62 is made in the processing of step S20 and of step S50.The flowchart of FIG. 12 is different from that of FIG. 5 in that adetermination relating to the operating position of the shift lever 63is made in the processing of step S20 and of step S50.

Specifically, in FIG. 11, after it was determined to be underregeneration control in step S10, a determination is made as to whetheror not the parking brake 62 is operated to be at the braking position onthe basis of the detected signal of the parking brake operating positiondetecting means 66 (S20). When it is determined that the parking brake62 is operated to be at the braking position and it is determined thatthe exhaust gas temperature is lower than a threshold value in step S30,the temperature-rising assistance is started in step S40.

After the temperature-rising assistance has been started, when at leastone of condition 1, condition 2 (the parking bake 62 being at thebraking position) and condition 3 is determined as negative, thetemperature-rising assistance is stopped in step S60.

In FIG. 12, after it was determined to be under regeneration control instep S10, a determination is made as to whether or not the shift lever63 is operated to be at the neutral position N on the basis of thedetected signal of the shift lever operating position detecting device67 (step S20). When it is determined that the shift lever 63 is operatedto be at the neutral position N and that the exhaust gas temperature islower than a threshold value in step S30, the temperature-risingassistance is started in step S40.

After the temperature-rising assistance has been started, when at leastone of condition 1, condition 2 (the shift lever 63 being at the neutralposition) and condition 3 is determined as negative, thetemperature-rising assistance is stopped in step S60.

Also the embodiment configured as described above can produce the sameeffects as the effects (a), (b) and (c) of the first embodiment.

(a) The exhaust gas cleaning system according to the present embodimentstarts the temperature-rising assistance on the basis of the brakingposition of the parking brake 62 or the neutral position N of the shiftlever 63. When operating the parking brake 62 to be at the brakingposition or the shift lever 63 to be at the neutral position N, theoperator intends to allow the wheel loader not to travel. In this case,the period of time during which the engine output lowers becomes long.When the engine output lowers, exhaust gas temperature gradually lowersand is likely to become lower the threshold value. That is to say, theexhaust gas cleaning system according to the present embodiment startsthe temperature-rising assistance only when necessary. Thus, unnecessarytemperature-rising assistance can be avoided.

(b) When engine output lowers, it is gradually that the exhaust gastemperature lowers; however, it is not immediately that the exhaust gastemperature lowers. When the exhaust gas temperature is equal to orhigher than a threshold value, the temperature-rising assistance is notnecessary. The exhaust gas cleaning system according to the embodimentis provided with the exhaust gas temperature detecting device 37. Whenthe exhaust gas temperature detected by the exhaust temperaturedetecting device 37 is equal to or higher than the threshold value, thetemperature-rising assistance is not done. This can further avoidunnecessary temperature-rising assistance.

(c) The exhaust gas purifying system according to the present embodimentcommands the stop of the temperature-rising assistance on the basis ofthe braking-releasing position of the parking brake 62 or the forwardmovement position F or rearward movement position R of the shift lever63. An interval of time until the resuming of the travel by theaccelerator pedal 61 after the command of stopping thetemperature-rising assistance by the parking brake 62 or by the shiftlever 63, that is to say, an interval of time until the accelerator 61is operated after the operator operates the parking brake 62 or theshift lever 63 to enable the wheel loader to be traveled, is longer thanthe response time of the control valve 30 or of the regulator of thepump 11. At the time of resuming the travel, the engine output isreturned to the engine output PS1 (the pump discharge pressure P1 andthe pump discharge amount Q1). Thus, the degradation in operability inresuming the traveling can be prevented.

What is claimed is:
 1. A hydraulic excavator comprising: a dieselengine; a hydraulic pump driven by the engine; a plurality of actuatorsdriven by a hydraulic fluid discharged from the hydraulic pump fordriving a plurality of driven bodies; a plurality of operating leverunits for commanding the driven bodies to operate; a plurality of flowcontrol valves activated by said plurality of operating lever units forcontrolling flow of the hydraulic fluid supplied from the hydraulic pumpto said plurality of actuators; operation stopping means for disablingthe operation of the driven bodies even if the operating lever units areoperated; and an exhaust gas cleaning system, wherein the exhaust gascleaning system includes: a filter device disposed in an exhaust systemof the engine and including a filter for capturing particulate mattercontained in exhaust gas; a regeneration device having an oxidationcatalyst and configured to supply unburned fuel to the oxidationcatalyst to increase temperature of the exhaust gas thereby to burn andremove particulate matter deposited on the filter; and a regenerationcontrol device configured to control the start and stop of operation ofthe regeneration device, wherein the operation stopping means includes agate lock lever selectively operable between a first position to limitan entrance to a cab seat and a second position to open the entrance tothe cab seat and configured such that, when the gate lock lever islocated in the first position, the operation of said plurality of flowcontrol valves by said plurality of operating lever units is enabledthereby to enable the operation of said plurality of actuators to drivesaid driven bodies and, when the gate lock lever is operated from thefirst position to the second position, the operation of said pluralityof flow control valves by said plurality of operating lever units isdisabled thereby to disable the operation of said plurality of actuatorsto drive the driven bodies, wherein the exhaust gas cleaning systemfurther includes temperature-rising assistance device for assistingtemperature-rising of the regeneration device by increasing at least oneof the discharge pressure and discharge amount of the hydraulic pump soas to apply a hydraulic load to the engine thereby to increase thetemperature of the exhaust gas and oxidize the unburned fuel with theoxidation catalyst, and wherein the regeneration control device isconfigured to start the operation of the temperature-rising assistancedevice when the gate lock lever is operated from the first position tothe second position during the operation of the regeneration device. 2.The hydraulic excavator according to claim 1, wherein the regenerationcontrol device is configured to stop the operation of thetemperature-rising assistance means when the gate lock lever is operatedfrom the second position to the first position to release disabling ofthe driving of said plurality of actuators and release the stop of theoperation of the driven bodies.
 3. The hydraulic excavator according toclaim 1, wherein the temperature-rising assistance includes a controlvalve installed on a downstream side of a center bypass line connectingsaid plurality of control valves in series and having an open positionand a closed position, and wherein the regeneration control device isconfigured to apply the hydraulic load to the engine by switching thecontrol valve from the open position to the closed position.